Optimization Of Injection-production Parameters For In-situ Combustion Reservoirs By Considering Multiple Mechanisms

The adjustment of injection-production parameters determines the effect of EOR.At present,the consideration of all kinds of factors in adjustment injection-production parameters of in-situ combustion is mostly not comprehensive enough.Therefore,it is necessary to further study the combination of multiple mechanism of in-situ combustion and the field parameter adjustment.In order to design and adjust injection-production parameters more quickly and accurately,and further clarify the direction of injection-production parameters adjustment,the following research has been done in this paper.(1)This paper quantitatively analysis the contribution of each mechanism of in-situ combustion to oil recovery to screen out the main mechanism and analysis production characteristics under different conditions.The results show that the main mechanism of in-situ combustion is heating viscosity reduction and reaction modification.The mechanism related to thermal energy accounts for about 90%of the total contribution,and the rigid gas drive accounts for 10%can't be ignored.Reservoir temperature has great influence on production stage.Gas injection rate,reservoir temperature and chemical reaction rate have great influence on final recovery factor.The higher the reservoir temperature,the higher the permeability and the lower the viscosity of heavy oil,the shorter the effective time and shut-in time of producer.(2)The applicability of four calculation methods of injection-production parameters is analyzed,which includes experimental method of combustion tube,gas injection rate based on combustion demand,material balance and energy balance equation.The relationship between gas injection rate and correlative factors in various methods is analyzed.An optimization method of injection-production parameters is established,which is mainly based on the relationship between speed of advance of fire line and the gas injection rate.(3)On the basis of the relationship between speed of advance of fire line and the gas injection rate,the characteristic plate of in-situ combustion is established under the constraints of oxygen utilization rate,pressure build-up rate,oxygen demand for combustion and volume sweep efficiency.The injection-production coordination interval can be obtained from checking the characteristic plate.Subdividing the plate into regions and analyzing the characteristics of each region,the injection-production coordination interval is obtained.In order to extend the characteristic plate apply to other working conditions,the dimensionless characteristic plate is established by replacing gas injection rate with ventilation intensity.(4)The optimization method of injection-production parameters in two situations,the stage of scheme design and after start-up of in-situ combustion,is established.The latter optimization method uses the characteristic plate of in-situ combustion and be validated feasibility through numerical simulation.Guided by plate,it is more reasonable to adjust the gas injection rate to about 12,500 m~3/d in the fourth layer of Du66W area after three years of development.And it is recommended to design and optimize injection-production parameters with ventilation intensity of 1.105 m3/(m2·h)in whole Du66W area.